Energy Conversion & Combustion Group

Departamento de Industriashttp://www.industrias.usm.cl
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EC2G group members attended Ninth Mediterranean Combustion Symposium


Jorge Contreras, Felipe Escudero and Rodrigo Demarco have been present at the symposium, showing their works. The Symposium occurred on 7th-11th of June in Rhodes, Greece.


Felipe Escudero has presented his paper as part of the master program (MII) imparted at Universidad Federico Santa María and Jorge Contreras as part of his PhD program in France.


Dr. Demarco, Lecturer of EC2G group, has shown his result as part of the "(REDES130090) Energy Conversion: Application to Flame Radiation and Soot Production" project.




ON THE STRUCTURE OF MICROGRAVITY SOOTING LAMINAR BOUNDARY LAYER DIFFUSION FLAMES AND ITS IMPACT ON RADIATIVE TRANSFER

J. Contreras, J.L. Consalvi, A. Fuentes, F. Liu.


Abstract

Two microgravity ethylene laminar boundary layer diffusion flames generated by a flat porous burner and characterized by the fuel injection velocities  of 3 and 4 mm/s and an oxidizer velocity of 250 mm/s have been simulated by using an accurate radiation model, a comprehensive kinetic mechanism, and a  soot model consisting of inception as a result of the collision of two pyrene molecules, heterogeneous surface growth and oxidation following the hydrogen  abstraction acetylene addition (HACA) mechanism, soot particle coagulation, and PAH surface condensation. Model predictions are in reasonable agreement with the experimental data in terms of the stand-off distance and soot volume fraction. The stand-off distance and soot production are enhanced as the fuel velocity increases. H and OH radicals, responsible of the de-hydrogenation of sites in the HACA process, and pyrene, of the species for soot inception and PAH condensation processes, are found to be located in a region that follows the stand-off distance. Soot is then produced in this region and is transported inside the boundary layer by convection and thermophoresis. Radiative loss is substantially higher in these flames than in normal gravity diffusion flames owing to much longer residence times. Calculations carried out by neglecting soot radiation and by using the optically-thin approximation  (OTA) revealed that soot dominates the radiative heat transfer in these flames and that the use of OTA gives rise to significant discrepancies in temperature and soot volume fraction.



EFFECTS OF OXYGEN INDEX ON SOOT PRODUCTION AND TEMPERATURE IN AN ETHYLENE INVERSE DIFFUSION FLAME

F. Escudero, A. Fuentes , R. Demarco, J.-L. Consalvi, F. Liu, J.C. Elicer-Cortés, A.C. Fernandez-Pello


Abstract

An experimental study was conducted to investigate the effects of the Oxygen Index (OI) in an ethylene laminar inverse diffusion flame (IDF). The OI was varied from 21% to 37% and its influence was measured in terms of flame height, soot volume fraction, soot temperature and radiant fraction. Stoichiometric flame height was measured by spontaneous emission of CH* radicals and was found to decrease when the OI increases. In contrast, the luminous flame height increases with OI because soot can still form and grow beyond the reaction zone. Radial profiles of soot volume fraction and soot temperature were evaluated by means of a Modulated Absorption/Emission (MAE) technique. The line-of-sight intensities, integrated along the optical path and captured by ECCD at two wavelengths were inverted using deconvolution and regularization techniques in order to obtain radial profiles of soot volume fraction and temperature. The increase in OI enhances soot volume fraction due to higher temperatures and soot formation rates. Both the local and integrated soot quantities increase with OI. The radiant fraction of IDF increases with OI in a similar way to the integrated soot volume fraction.



NUMERICAL STUDY OF OXYGEN INDEX ON SOOT PRODUCTION AND RADIATION IN ETHYLENE INVERSE DIFFUSION FLAMES

R. Demarco, A. Antinao, K. Munoz-Feucht, J.L. Consalvi, F. Nmira and A. Fuentes.


Abstract

A numerical study was carried out in order to obtain insights into the e effects of the oxygen concentration of the oxidant stream, called Oxygen Index (OI), on the soot production and on the flame radiation in laminar Inverse Diffusion Flames (IDF). Ten axisymmetric laminar IDF were simulated, varying the OI of the oxidant stream from 17% to 35%. All the flames were fueled with pure ethylene, which was kept at a constant volumetric flow rate for all cases. The oxidant flux was also kept at a constant flow rate, but the oxygen concentration was varied. Simulations were compared with experimental data. Flame height, soot volume fraction, radially integrated soot volume fraction, temperature and radiant fraction were studied. Comparison were intended to assess the capabilities of a relatively fast numerical code, based on Steady Laminar Flamelet (SLF) model, a two-equation acetylene/benzene-based semiempirical soot formation model and a Full- Spectrum correlated-k (FSCK) radiative property model. Higher OI were found to generate shorter flames, presenting higher temperatures and an increase in the soot production and energy irradiated. Results show that the simulations predict correctly the experimental behavior observed by changing the OI. Flame heights were all well predicted. Roper theory can be adapted to account for estimating flame height in IDF conditions. Simultations in terms of soot volume fraction, integrated soot volume fraction and radiant fractions are in good agreement with the experiments up to OI=25%. For higher OI, an increasing overprediction with OI was observed.